1. I dont have the fade.png file, I dont know how it is.
2. I've taken a look to the code and I see that it is a particle that atracts other ones than appears in a random way throught the windows. I´ve modified the code to represent the particles as a point instead of using the fade.png. The particles appears at the beginning and all dissapear quickly. I´ve changed the atraction constant and they dissapear slowly, but they don't move. I vave no idea of why this is happening.